Plymouth-based medical device maker Urotronic is ramping up clinical research on its Optilume drug-coated balloon to treat men with narrowed urethras, accelerating the data-gathering process for its novel device.

The Optilume is an investigational device used during an outpatient medical procedure to treat a urethral stricture. Urologists have long used mechanical dilation, but many men end up needing a later procedure because of re-narrowing. The Optilume is designed to deliver an anti-inflammatory drug into the urethra after dilation to prevent recurrence.

The Optilume is not yet approved by the Food and Drug Administration (FDA), but Urotronic hopes that its ongoing clinical studies can gather the evidence needed to show that it is safe and effective in treating stubborn urethral strictures.

Urotronic said there are about 1.5 million U.S. doctor visits a year to treat urethral strictures, which happen when the urinary tract is damaged by trauma, infection or medical procedures. Scar tissue in the urethra builds into a stricture that can block the flow of urine from the bladder, making it more difficult and sometimes painful to urinate. Older men are considered more at-risk urinary-tract problems like strictures.

This week Urotronic announced that the FDA has approved a pivotal trial for its Optilume device. Called Robust III, the trial will randomize at least 140 men to get either the Optilume balloon treatment or a control treatment that is considered the best standard of care for the study site and participant. The first 60 patients will be evaluated at six months in an interim analysis that will determine how many more patients will need to be enrolled, with a ceiling of 200.

The study will include patients at up to 20 different sites, including the University of Minnesota. Patients need to have had at least two prior dilation treatments for the same stricture before they can join the trial. Patients will be blinded as to whether they have been treated with traditional mechanical dilation or an Optilume balloon.

"I would hope that the Urotronic balloon device falls into a good middle ground, where it can offer better success rates than plain balloon dilation but is less invasive than urethroplasty, which is the plastic-surgical rebuilding of the urethra," said University of Minnesota urologist Dr. Sean Elliott, a principal investigator with the trial. (Elliott said he has served as a paid consultant to Urotronic in the past but is not a consultant today.)

Technically, Urotronic will have more than one ongoing U.S. clinical trial for the Optilume.

A U.S. feasibility trial called Robust II is already enrolling 15 patients at five U.S. sites. The much larger Robust III trial will be ongoing simultaneously but at more sites and with more treating physicians. Elliott said that at the U, which is a site for both trials, enrollment for Robust II will be completed before new patients are enrolled in Robust III.

The FDA approved Urotronic's Robust III trial even though Robust II will still be ongoing, based partly on positive data that were reported out of a smaller, ongoing trial called, yes, Robust I.

Robust I, which is examining treatment-resistant patients in the Dominican Republic and Panama, found that 76 percent of the patients had not had a recurrence six months after being treated with the Optilume, Elliott said.

Since these are high-risk patients with at least three previous treatment failures, about 80 percent of them would have been predicted to have experienced a recurrence by six months if they had gone through another traditional mechanical dilation, Elliott said.

"We hope to repeat the compelling clinical results from our Robust I Latin America study with the pending U.S. Pivotal study and demonstrate a minimally invasive treatment option that can be performed in a variety of clinical settings, including as an in-office procedure," Urotronic Chief Executive David Perry said in a news release.

Joe Carlson writes about medical technology in Minnesota for the Star Tribune.